The invention relates to a method for adjusting the pressure in pneumatic tires, in particular in pneumatic tires of an agricultural vehicle.
The ideal tire pressure varies greatly in agricultural vehicles, depending on operating conditions. In the case of road travel, high tire pressures ensure that the rolling friction and flexing work carried out at the tires is minimal. This results in forward motion that is energy-efficient and gentle on material. A much lower tire pressure is desirable for field work, however, in order to distribute the weight of the vehicle across a large ground contact area and thereby minimize soil compression and, to allow the tire profile to adapt to the ground and thereby permit efficient transfer of the drive force. It is therefore desirable per se to adjust the tire pressure whenever switching between road travel and field work. If the vehicle driver must spend too much work time adjusting the tire pressure, however, it can be assumed that such adjustment at said switching will not be carried out, or rarely carried out.
Patent document DE 10 2009 051 403 A1 makes known a tire pressure monitoring system for a vehicle, in which all the vehicle tires are connected to a common distribution line. The distribution line is connected to a pressure accumulator via a control valve and a throttle. The direction of an air flow through the throttle can be detected with the aid of pressure sensors disposed on either side of the throttle. When the air flow comes to a halt, the pressure in the tires has reached the same level as that of the pressure accumulator, the tire valves and the control valve can be closed and the tires can be disconnected from the distribution line. Since the pressure differential between the tires and the pressure accumulator diminishes continuously over time as tire pressure is adapted using this conventional system, the air flow also slows down and the time required for pressure to equalize is long.
Additionally, agricultural vehicles such as combine harvesters or tractors in particular often comprise tires of different sizes at the rear and front axles, wherein the tires are operated using different pressures. In order to adjust the pressure thereof, the pressure accumulator must be set to two different pressures, one after the other, which greatly extends the duration of the pressure-adaptation procedure.
A further known problem is that the vehicle tilts when the pressure is adjusted at the front and rear axles of the vehicle one after the other. If the vehicle is a tractor having a soil management tool, such as a plow, a cultivator or the like mounted thereon, the tilting motion results in a change in the depth to which the working tool extends into the soil. If the tractor moves during this time, then the soil management carried out during the pressure adjustment will be faulty due to the fluctuation in the engagement depth. Therefore, the vehicle must be at a standstill when the pressure adjustment is carried out and the driver must spend working time therefor.